This invention relates to a picture encoding apparatus and the method, and is applicable to a picture encoding apparatus, for example, for dividing a predetermined picture data into a plurality of picture data having various resolutions and encoding it.
Heretofore, a picture encoding apparatus for encoding input picture data using a method of hierarchy encoding, for example, pyramid encoding has been provided. In this type of picture encoding apparatus, a first hierarchy data being input picture data of high resolution, a second hierarchy data of which its resolution is lower than that of the first hierarchy data, and a third hierarchy data of which its resolution is lower than that of the second hierarchy data, are sequentially and recursively formed. The plurality of hierarchy data are transmitted through one transmitting path being a communicating path or a recording/reproducing route.
In a picture decoding apparatus for decoding this plurality of hierarchy data, all of the plural picture data can be decoded, in addition to this, one of the desired hierarchy data can be selected and decoded in accordance with the resolution of the corresponding television monitor or the like. In this manner, only the desired hierarchy data is decoded out of the plurality of hierarchy data, so that the desired picture data can be obtained with the minimum amount of transmitting data at need.
Here, as shown in FIG. 1, in the hierarchy encoding, a picture encoding apparatus 1 for actualizing for example, four hierarchical-encoding, has decimating filters 2, 3, and 4 of three hierarchies and interpolating filters 5, 6, and 7. The input picture data D1 is passed through the decimating filters 2, 3, and 4 of the respective stages to sequentially form reduced picture data D2, D3, and D4 having a lower resolution, and the reduced picture data D2, D3, and D4 are passed through the interpolating filters 5, 6, and 7 to change the resolutions of those data to that before reducing.
Outputs D2 to D4 of the respective decimating filters 2 to 4 and outputs D5 to D7 of the respective interpolating filters 5 to 7 are input to difference circuits 8, 9, and 10 respectively, in order to generate difference data D8, D9, and D10. As a result, in the picture encoding apparatus 1, the data quantity of hierarchy data and the signal power are reduced. Here, the difference data D8 to D10 and the reduced picture data D4 have the sizes of 1, xc2xc, {fraction (1/16)}, and {fraction (1/64+L )} respectively in the areas.
The difference data D8 to D10 obtained from the difference circuits 8 to 10 and the reduced picture data D4 obtained from the decimating filter 4, are encoded by respective encoders 11, 12, 13, and 14 and are performed compression processing. As a result, first, second, third, and fourth hierarchy data D11, D12, D13, and D14 which have different resolutions respectively are sent from the respective encoders 11, 12, 13, and 14 to a transmitting path in a predetermined sequence.
Thus transmitted first through fourth hierarchy data D11 through D14 are decoded by a picture decoding apparatus 20 shown in FIG. 2. That is, the first through fourth hierarchy data D11 through D14 are decoded by decoders 21, 22, 23, and 24 respectively, so that the fourth hierarchy data D24 is output from the decoder 24.
Further, in an adding circuit 29, the output of the decoder 23 is added to the interpolating data of the fourth hierarchy data D24 obtained from an interpolating filter 26, to restore the third hierarchy data D23. Similarly, in an adding circuit 30, the output of the decoder 22 is added to the interpolating data of the third hierarchy data D23 obtained from an interpolating filter 27, to restore the second hierarchy data D22. Further, in an adding circuit 31, the output of the decoder 21 is added to the interpolating data of the second hierarchy data D22 obtained from an interpolating filter 28, to restore the first hierarchy data D21.
However, in a picture encoding apparatus realizing the above method of hierarchy encoding, the input picture data is divided into a plurality of hierarchy data and encoding it, hence, the amount of data of the hierarchy component is increased necessarily, as a result, it arises that compression efficiency decreases comparing with the case of using the high-efficiency encoding system in which hierarchy encoding is not used. Further, there is a problem that when improving the compression efficiency, the deterioration of picture quality occurs due to the respective quantizers applied to the hierarchy data.
Considering the above points, this invention provides a picture encoding apparatus such that when picture data is encoded hierarchically, the compression efficiency can be improved, and deterioration of picture quality can be reduced.
To solve such problems, according to this invention, as a first embodiment, a picture encoding apparatus 40 for encoding input picture data D31 to generate a plurality of hierarchy data D51 to D55 which have recursively various resolutions, comprises: means 53C, 55C, . . . , 53D, 55D, . . . for determining the quantization characteristic of the lower hierarchy data which has a resolution higher than that of the upper hierarchy data based on the activity of the upper hierarchy data having lower resolution in order to quantize respective hierarchy data D44, D43, D42, and D41; and a quantizing means 53A, 55A, . . . for quantizing respective hierarchy data in accordance with the determined quantizing characteristic.
Further, according to this invention, as a second embodiment, the picture encoding apparatus 40 for sequentially encoding input picture signal D1 to generate a plurality of hierarchy data D51 to D55 which have recursively various resolutions, comprises: means 53C, 55C, . . . , 53D, 55D, . . . for determining the quantized value of the hierarchy data in the block to be quantized based on the quantization step width E0, E1, E2, or E3 determined by the upper hierarchy data having a resolution lower than that of the hierarchy data D44, D43, D42, or D41 in the block to be quantized for each block corresponding to one another in each hierarchy, in order to quantize the hierarchy data D44, D43, D42, D41 respectively; and a quantizing means 53C, 55C, . . . , 53D, 55D, . . . for determining the quantization step width E0, E1, E2, or E3 of the lower hierarchy data which have a resolution higher than that of the hierarchy data in the block to be quantized.
Further, according to this invention, as a third embodiment, a picture encoding apparatus 60 for sequentially encoding input picture signal to generate a plurality of hierarchy data D51 to D55 which have recursively various resolutions, comprises: means 53C, 55C, . . . , 53D, 55D, . . . for determining the quantized value of the hierarchy data in the block to be quantized based on the quantization step width E0, E1, E2, or E3 determined by the upper hierarchy data having a resolution lower than that of the hierarchy data D44, D43, D42, or D41 in the block to be quantized in order to quantize the respective hierarchy data D44, D43, D42, D41, and for determining the quantization step width E0, E1, E2, or E3 of the lower hierarchy data having a resolution higher than that of the upper hierarchy data based on a historical information of the distribution of the quantized value of the hierarchy data upper than the lower hierarchy data having a resolution higher than that of the hierarchy data in the block to be quantized.
Further, according to this invention, as a fourth embodiment, a picture encoding apparatus 70 for encoding input picture data D31 to generate a plurality of hierarchy data D51 to D55 which have recursively various resolutions, comprises: determination means 53E, 55E, . . . for determining the number of quantizing bits of the lower hierarchy data having a resolution higher than that of the hierarchy data in the block to be quantized for each block corresponding to one another between hierarchies, based on the quantization step width E0, E1, E2, or E3 determined by the upper hierarchy data having a resolution lower than that of the hierarchy data in the block to be quantized; and quantizing means 53A, 55A, . . . for quantizing respective hierarchy data in accordance with the number of the determined quantizing bits.
Further, according to this invention, as a fifth embodiment, a picture encoding apparatus 80 for encoding the input picture data D31 to successively generate a plurality of hierarchy data D51 to D55 having various different resolutions recursively comprises: means 49, 51, 53, 55, 57, and 81 for determining the quantization step width of the lower hierarchy data D35 having lower resolution than that of the upper hierarchy data based on the quantization step width EO, El, E2, or E3 determined in the upper hierarchy having lower resolution in every predetermined block of respective hierarchy data to quantize respective hierarchy data D44, D43, D42, and D41 respectively and for determining the uppermost hierarchy data D35 having lowermost resolution to fixed quantization step width PA; and quantizing means 53A, 55A, . . . for quantizing respective hierarchy data in accordance with each quantization step width PA, E0, E1, E2, E3.
According to this invention, in a picture encoding apparatus 40 for sequentially and recursively generating a plurality of hierarchy data D51 to D54 having a plurality of different resolutions from a picture data D31, the quantization step width E0, E1, E2, or E3 of a lower hierarchy data of which the resolution is higher than the upper hierarchy data, is determined in order to omit additional codes showing the characteristic of the quantizers, so that the picture encoding apparatus 40 in which the compression efficiency in hierarchy-encoding can be improved, and the deterioration of the picture quality can be reduced, can be realized.
According to this invention, when the quantization step width E1, E2, E3 of the lower hierarchy data is determined, the gain which is multiplied by the quantization step width E0, E1, E2 of the upper hierarchy data adjacent to the lower hierarchy data, is determined with reference to the historical information of the selected result of the gain in the upper hierarchy data prior to the result in the lower hierarchy data, so that the suitable quantization step width can be obtained for respective hierarchy data, and a picture encoding apparatus 60 in which the deterioration of picture quality can be reduced, can be realized.
According to this invention, in a picture encoding apparatus 70 for sequentially and recursively generating a plurality of hierarchy data D51 to D54 having a plurality of different resolutions from input picture data D31, the quantization bit number of a lower hierarchy data having a resolution higher than the upper hierarchy data is determined for each of the predetermined blocks of respective hierarchy data D44, D43, D42, D41 based on the quantization step width E0, E1, E2, E3 determined in the upper hierarchy data having a lower resolution, so that the quantization bit number can be adaptively determined by using the relation between adjacent hierarchies. Thereby, the transmitting bit number can be effectively reduced without deteriorating the picture quality, and a picture encoding apparatus 70 such that, the compression efficiency can be improved, can be realized.
According to this invention, in a picture encoding apparatus 80 for sequentially and recursively generating a plurality of hierarchy data D51 to D54 having a plurality of different resolutions from input picture data D31, when a plurality of hierarchy data is encoded, the quantization step width E1, E2, E3 of the lower hierarchy data having a resolution of which is higher than that of the upper hierarchy data is determined for each predetermined block of hierarchy data D44, D43, D42, D41, based on the quantization step width E0, E1, E2, E3 determined by the upper hierarchy data having low resolution, and the quantization step width P in quantizing the uppermost hierarchy data D35 having a lowest resolution is generated by calculating the pixel value of pixel to be quantized contained in the block to be quantized of the uppermost hierarchy data and the pixel value of the neighboring pixel near the pixel to be quantized, so that the quantization step width in respective hierarchy data can be determined to a value which is suitable to respective hierarchy data. Therefore, the picture encoding apparatus 80, in which the deterioration of the picture quality can be reduced in quantizing, can be realized.